Cannabis use by adolescents linked to lasting cognitive changes

Cannabis use was linked to simultaneous and lasting changes in adolescent cognitive function, according to a study that tracks Canadian high school students for four years.

Patricia Conrod, Ph.D., Ph.D., of the CHU Sainte-Justine Research Center at the Université de Montréal, indicated that cannabis use, but not alcohol consumption, was related to delayed changes in inhibitory control and working memory, as well as concomitant changes in delayed memory recall and perceptual reasoning. , in the American Journal of Psychiatry.

While cannabis and alcohol use was linked to generally lower performance in all cognitive domains, "there was particular concern that cannabis use was associated with lasting effects on a measure of inhibitory control, risk factor for other addictive behaviors, and could explain why early cannabis use is a risk factor for other addictions, "Conrod said in a statement.

This study, one of the first to track the evolution of cannabis use among young people while repeatedly testing their cognitive function, brings "a drastic change from what we've know about cannabis and mental abilities, "noted Terrie Moffitt, PhD, of Duke University, not involved in research.

"The issue has been very controversial, because of concern that legalization places more cannabis in the hands of more juvenile users," Moffitt said. MedPage today.

"Skeptics argue that cannabis appears alongside low mental abilities simply because it is the least able-bodied adolescents who are most likely to use cannabis of this generation.This study has shown evidence of this, but The study also revealed that their critical mental abilities declined over time, as students used cannabis for several years. "

Rod and co-authors followed 3,826 Canadian teens who participated in an annual online survey to assess cognition, alcohol, and cannabis use (using a 6-point scale). points ranging from "never" to "every day") for 4 years Researchers examined the relationships between annual variations in psychoactive substance use and recall memory, perceptual reasoning, inhibition and the working memory and used multilevel regression models to test vulnerability and simultaneous and sustainable changes in each cognitive domain.

The average frequency of cannabis use over 4 years predicts a lower performance on working memory (Beta 0.51, SE 0.25, P= 0.04), perceptual reasoning (Beta -0.25, SE 0.08, P= 0.001) and inhibition (Beta 1.19, SE 0.48, P<0.01) over the same period.

Any increase in the frequency of cannabis use was associated with an alteration of delayed recall memory in the same person in the same year (Beta -0.14, SE 0.05, P<0.01) and further degradation of the inhibitory task one year later (Beta 1.05, SE 0.41, P= 0.01). A similar, but marginal, shifted association emerged for working memory (Beta 0.36, SE 0.19, P= 0.06).

While the average amount and frequency of alcohol consumption over 4 years was broadly related to lower spatial work memory performance, lower perception reasoning scores and more errors in the inhibitory control task, no intra-subject alteration was of significance for any of the cognitive domains studied. .

This study used data from the Co-Venture Study, a longitudinal, randomized controlled trial of a targeted drug and alcohol intervention among students in 31 high schools in the Montreal area. . All participants, regardless of the exposure to the intervention, were included in the analysis.

The use of cannabis and undeclared and self-reported alcohol is an important limitation of the study. The amount or dose of exposure to cannabis also could not be measured. Although research staff are closely monitoring cognitive function tests, it would be important to link these findings to standardized results in high school exams or other academic outcomes, the researchers noted.

2018-03-10T00: 00: 00-0500

Last update 03/10/2018